The present invention relates generally to a tone information processing apparatus and method for converting a pitch (tone pitch) of tone information in accordance with a chord, as well as a storage medium storing a computer-executable program related to the method.
Electronic keyboard instruments have been known which have an automatic accompaniment function (style reproduction function) for converting a pitch of each of notes, which are included in an accompaniment pattern of a plurality of performance parts prestored in accompaniment style data classified per music genre like jazz or rock, in accordance with a chord designated during reproduction. Each accompaniment pattern for use in such an automatic accompaniment function is a pattern created so as to arrange accompaniment notes of pitches based on a desired reference chord. In association with such an accompaniment pattern, a note conversion table is prepared in advance for converting each pitch within the accompaniment pattern into a pitch corresponding to a chord designated during reproduction. More specifically, pitch shift data corresponding to a designated chord type are read out on the basis of the note conversion table, and pitches of individual accompaniment notes included in the accompaniment pattern are converted into pitches corresponding to the designated chord (see Japanese Patent Application Laid-open Publication No. HEI-10-293586 (hereinafter referred to as “Patent Literature 1”)).
In the case of timbres or colors of sustained tones, such as certain types of folk instrument tone colors, for example, there is often used an expression that, during a sounding time period of a tone, varies the tone from a certain pitch to another pitch in a continuous manner. In order to create accompaniment pattern data having a realistic performance expression by use of such a sustained-tone color, it is necessary to include, in the accompaniment pattern data, an expression that, during a sounding time period of a given tone, continuously varies the pitch of the tone. However, with the automatic accompaniment function disclosed in Patent Literature 1, it is not possible to include, in accompaniment pattern data, tone information that, during a sounding time period of a given tone, continuously varies the tone from a certain pitch to another by a pitch bend or the like.
More specifically, if the accompaniment pattern includes tone information representative or indicative of a tone continuously varying in pitch by a pitch bend or the like, the pitch conversion technique disclosed in Patent Literature 1 would perform pitch conversion only in accordance with a shift amount corresponding to a note number (pitch) with no regard to the pitch bend or the like instructed halfway through the sounding time period. Thus, the expression of continuous pitch variation by the pitch bend or the like would not match the type of the designated chord. For example, in a case where an accompaniment pattern created on the basis of a C major chord includes a pitch bend that varies a pitch auditorily for four semitones from a C note to an E note, and if a C minor chord has been designated during reproduction, the pitch conversion technique disclosed in Patent Literature 1 can only effect pitch variation auditorily for four semitones from the C note to the E note although a user wants a pitch bend to be performed auditorily for three semitones from the C note to an E flat note.
Further, Japanese Patent Application Laid-open publication No. 2004-170840 (hereinafter referred to as “Patent Literature 2”) discloses a technique for continuously varying a pitch in accordance with a designated chord. According to the disclosure of Patent Literature 2, when a pitch of a performance input note is to be automatically converted in accordance with a chord change instruction included in currently reproduced sequence data (automatic performance data), and if the performance input note is of a sustained-tone color, for example, continuous variation from the currently-sounded pitch to another pitch is effected in accordance with the chord change instruction and using for example a pitch bend, without silencing the currently-sounded tone. If, on the other hand, the currently-generated tone is not of a sustained-tone color, then the currently-generated tone is deadened or silenced and then the tone is re-generated after being converted into the other pitch matching the chord change instruction.
According to the technique disclosed in Patent Literature 2, however, only one pitch is associated with a performance input note that functions as a basis of pitch conversion, and no consideration is given at all to a situation where “a performance input note continuously varies from a certain pitch to another pitch during a sounding time period of the input note” or “an expression for continuously varying a performance input note from a certain pitch to another pitch during the sounding time period of the input note is imparted to the input note”. Therefore, with the technique disclosed in Patent Literature 2 too, pitch conversion cannot be performed appropriately in accordance with a designated chord in a case where a performance input note continuously varies from a certain pitch to another pitch during the sounding time period of the input note.
Further, Japanese Patent Application Laid-open publication No. 2007-293373 (hereinafter referred to as “Patent Literature 3”) discloses a technique for converting pitches of an arpeggio pattern prepared in a waveform data format. According to the technique disclosed in Patent Literature 3, a plurality of data sets are prepared in advance for an arpeggio pattern in association with a plurality of application ranges based on tempos, chord roots (root notes), chord types, etc, and each waveform data set indicative of any one of arpeggio patterns is divided in advance into segments corresponding to individual notes that constitute an arpeggio. Then, an arpeggio pattern (waveform data set) corresponding to user's performance input (user-designated tempo and chord) is read out, and a pitch of each of the segments of the read-out waveform data set is converted in accordance with the designated chord.
However, the technique disclosed in Patent Literature 3 is designed to segment a waveform data set per note included in the arpeggio and never assumes a case where the note continuously varies from a certain pitch to another during the sounding time period of the note. Thus, in a case where a tone (arpeggio component note) continuously varying in pitch during its sounding time period is included in an arpeggio pattern, the technique disclosed in Patent Literature 3, which executes pitch conversion on an arpeggio pattern of the waveform data format in accordance with a chord designated during reproduction of the arpeggio pattern, too cannot appropriately perform pitch conversion on the arpeggio pattern in accordance with a designated chord.